Amplification circuit, driver circuit for display, and display

Abstract

An amplification circuit includes: an amplifier apparatus configured to amplify an input signal and outputting the amplified signal from an output terminal; and a boost circuit which, when a difference between a voltage of the input signal and a voltage at the output terminal is greater than a given value, supplies a positive or negative constant electrical current to at least one given part of the amplifier apparatus, thus enhancing output responsiveness of the amplifier apparatus.

What is claimed is: 
     
       1. An amplification circuit comprising:
 an amplifier apparatus configured to amplify an input signal and output the amplified signal from an output terminal, the amplifier apparatus comprising an operational amplifier including a differential amplifier receiving the input signal and an output amplifier configured to amplify an output of the differential amplifier and provide an output signal at the output terminal, the output amplifier having a first capacitive element and a second capacitive element; and 
 a boost circuit connected to the differential amplifier and the output amplifier, and configured to compare a voltage of the input signal and a voltage at the output terminal with respect to a given value, the boost circuit being configured to supply a positive or negative constant electrical current to at least one of the first capacitive element and the second capacitive element of the amplifier apparatus, 
 wherein,
 the boost circuit is configured to electrically discharge one or both of the first and second capacitive elements when the voltage of the input signal is higher than the voltage at the output terminal by more than the given value, and 
 the boost circuit is configured to electrically charge one or both of the first and second capacitive elements when the voltage of the input signal is lower than the voltage at the output terminal by more than the given value. 
 
 
     
     
       2. The amplification circuit according to  claim 1 , wherein the operational amplifier includes a non-inverting input terminal and an inverting input terminal that receives input voltages to generate an output voltage through an output terminal. 
     
     
       3. The amplification circuit according to  claim 2 , wherein the operational amplifier includes a PMOS transistor, a NMOS transistor, the first capacitive element and the second capacitive element, the first capacitive element is connected between a gate and drain of the PMOS transistor, the second capacitive element is connected between the gate and drain of the NMOS transistor. 
     
     
       4. The amplification circuit according to  claim 3 , wherein a gate of the PMOS transistor is connected to an output terminal of the differential amplifier, the gate of the NMOS transistor is connected to another output terminal of the differential amplifier, a first output terminal of the boost circuit is connected to the gate of the NMOS transistor, a second output terminal of the boost circuit is connected to the gate of the PMOS transistor. 
     
     
       5. A driver circuit for a liquid crystal display, the driver circuit being operable to output a driver signal for driving each pixel formed in a display portion of the LCD for displaying an image, the driver circuit comprising:
 an amplifier apparatus configured to amplify an input signal and output the amplified signal from an output terminal, the amplifier apparatus being an operational amplifier including a differential amplifier and an output amplifier, the output amplifier having a first capacitive element and a second capacitive element, data lines of the display portion are connected to the output terminal; and 
 a boost circuit configured to compare a voltage of the input signal and a voltage at the output terminal with respect to a given value, the boost circuit being configured to supply a positive or negative constant electrical current to at least one of the first capacitive element and the second capacitive element of the amplifier apparatus, the driver circuit is provided for each data line of the display portion of the LCD, 
 wherein,
 the boost circuit is configured to electrically discharge one or both of the first and second capacitive elements when the voltage of the input signal is higher than the voltage at the output terminal by more than the given value, and 
 the boost circuit is configured to electrically charge one or both of the first and second capacitive elements when the voltage of the input signal is lower than the voltage at the output terminal by more than the given value. 
 
 
     
     
       6. The driver circuit according to  claim 5 , wherein the operational amplifier includes a non-inverting input terminal and an inverting input terminal that receives input voltages to generate an output voltage through the output terminal. 
     
     
       7. The driver circuit according to  claim 6 , the operational amplifier includes a PMOS transistor, an NMOS transistor, the first capacitive element and the second capacitive element, the first capacitive element is connected between a gate and drain of the PMOS transistor, the second capacitive element is connected between the gate and drain of the NMOS transistor. 
     
     
       8. The driver circuit according to  claim 7 , wherein a gate of the PMOS transistor is connected to an output terminal of the differential amplifier, the gate of the NMOS transistor is connected to another output terminal of the differential amplifier, a first output terminal of the boost circuit is connected to the gate of the NMOS transistor, a second output terminal of the boost circuit is connected to the gate of the PMOS transistor. 
     
     
       9. A display device having a driver circuit for outputting a driver signal used to drive each vertical pixel formed in a display portion configured to display an image,
 wherein, 
 the driver circuit has:
 an amplifier apparatus configured to amplify an input signal and output the amplified signal from an output terminal, the amplifier apparatus being an operational amplifier including a differential amplifier and an output amplifier, the output amplifier having a capacitive device; and 
 a boost circuit configured to compare a voltage of the input signal and a voltage at the output terminal with respect to a given value, the boost circuit being configured to supply a positive or negative constant electrical current to at least the capacitive device, and 
 the boost circuit is configured to electrically discharge the capacitive device when the voltage of the input signal is higher than the voltage at the output terminal by more than the given value, and 
 the boost circuit is configured to electrically charge the capacitive device when the voltage of the input signal is lower than the voltage at the output terminal by more than the given value. 
 
 
     
     
       10. The display device as set forth in  claim 9 , wherein:
 the differential amplifier is configured to amplify the input signal; and 
 the output amplifier has a transistor and the capacitive device, the transistor outputting a signal from the differential amplifier to the output terminal, and the capacitive device being connected between a gate of the transistor and the output terminal. 
 
     
     
       11. The display device as set forth in  claim 10 , wherein:
 the output amplifier has a transistor configured to output a signal from the differential amplifier to the output terminal, and 
 the boost circuit is configured to supply the constant current that is positive to a bias current supply node connected to the differential amplifier to increase a bias current for the differential amplifier, thus enhancing the output responsiveness of the amplifier apparatus. 
 
     
     
       12. The display device as set forth in  claim 10 , wherein:
 the output amplifier includes a first transistor and a second transistor, 
 the capacitive device includes a first capacitive element and a second capacitive element, the first capacitive element being connected between a gate of the first transistor and the output terminal, the second capacitive element being connected between a gate of the second transistor and the output terminal. 
 
     
     
       13. The display device as set forth in  claim 12 , wherein in the boost circuit,
 a first current mirror circuit, an output of a third transistor, and an output of a fourth transistor are sequentially connected in series between first and second potentials, 
 an output of a fifth transistor, an output of a sixth transistor, and a second current mirror circuit are sequentially connected in series between the first and second potentials, 
 the input signal is connected to a gate of the third transistor and to a gate of the sixth transistor, and 
 the output terminal is connected to a gate of the fourth transistor and to a gate of the fifth transistor. 
 
     
     
       14. The display device as set forth in  claim 9 , wherein the boost circuit only operates when the given value is exceeded.